Portable water treatment devices have become widely known and used in the home for removing contaminants from normal tap water. Such devices typically include a filter cartridge containing a purifying agent, such as activated charcoal. The filter cartridge has a limited life which is usually determined by the amount of water which can be filtered by the cartridge while maintaining a desired water quality. In this respect, after the rated life of a filter has been exceeded, the filtering characteristics of the filter deteriorate and some contaminants which the filter was designed to remove may remain in the filtered water. Thus, to ensure that a water treatment device operates at its maximum efficiency, it is necessary to monitor the number of uses of the device and replace the filter cartridge after the rated life of the filter cartridge has been reached.
Some existing water treatment devices suggest periodic replacement of a filter cartridge, such as on a monthly basis. Periodic replacement of a filter cartridge however, is unsatisfactory if the useful life of the filter cartridge is exceeded through heavy use of the device prior to the time for replacement. Still further, replacing a little used filter cartridge periodically is unnecessary and costly.
It is therefore desirable to accurately monitor the usage of the water treatment device to limit the volume of water filtered by the device to the rated volume of the filter cartridge. U.S. Pat. No. 4,986,901 to Nohren, Jr., et al., discloses a cap for a water treatment device having indicator means to keep track of how many times the treatment device in which the filter assembly is disposed has been filled and emptied. The indicator is manually advanced each time the treatment device is used. The problem with such device is that it is only accurate if the user remembers to advance the indicator wheel. Moreover, there is nothing to prohibit use of the device even after the maximum number of uses of the filter cartridge has been reached.
The present invention overcomes these and other problems and provides a portable water treatment device including means which automatically monitor use of the device, indicates when the life of the filter has exceeded its useful life, and deters further use of the treatment device.